London: Formula One teams have been warned against making `dummy` pitstops after Mercedes` failed attempt to fool Williams at the British Grand Prix.

With Brazilian Felipe Massa leading for Williams, the world champions had sent mechanics out into the pitlane as if in preparation for an early stop.

The aim was to hoodwink Williams into changing their strategy, by responding and bringing Massa in much earlier than scheduled, but that team saw the move for the ruse it really was and ignored it.

Mercedes escaped sanction for the attempted trickery but race director Charlie Whiting said on Thursday teams could face sanctions if they did it again.

"Going into the pit lane like this, for no valid reason, is not allowed but the difficulty would be proving it was a clear breach," said the International Automobile Federation (FIA) official.

"I have no intention of giving them a few chances and will talk to all the teams in Hungary about this and warning them that we will want to see (and hear) evidence that they were actually intending to stop."

The next race, the Hungarian Grand Prix, is on July 26.

The regulations state team personnel are only allowed in the pit lane "immediately before they are required to work on a car and must withdraw as soon as the work is complete" for safety reasons.

Mercedes motorsport head Toto Wolff, whose wife Susie is the Williams test driver, admitted at Silverstone that the team had been trying to fool their rivals.

"We know that Williams has more difficulties in keeping the tyres until the end and we knew that triggering an early stop on lap 18... would have caused them problems at the end. So it was a bit of a game, which didn`t function," he said.

"My wife sent me a WhatsApp (message) saying: "You guys think you can fool us? Hahaha". So it was worth at least the entertainment."

Wolff joked he would be dining alone later but the couple sent out a picture of themselves embracing in front of an Indian restaurant.

Whiting said no action had been taken at the time against Mercedes because it was not clear immediately whether they had planned to stop or not.

"In view of the fact that they were alleged to have said that it was a `dummy` stop they may have put their foot in it rather," he added.